Engine Stalling

[tackle51]

After driving my Model A for about 30 minutes and the tank is about half full it begins to act like it is running out of gas and stalls. Sometimes it will be idling smoothly in the driveway and just dies. It won't immediately re-start and I have been siphoning out the gas, cleaning the sediment bulb and the carburetor strainer. There is typically a fine sediment in the bulb and a little on the carb screen. This has been going on for some time and recently I installed a new fuel shut-off with a new in-tank screen, new interior gas line and a new line to the carburetor. Still no improvement! The carburetor was a rebuilt one about 2 years ago when the car was totally restored. The car starts easily and seems to run fine until stalling. Does anyone have any suggestions or recommendations? Thanks for the help.

[Big hammer]

Try running with the gas cap lose or removed,the gas cap may not be venting!

[Patrick L.]

Is the new fuel tank screen standard or is the inlet raised 1/2" or so ? Should be the latter.

Is the fuel inlet line in the carburetor too far ? Line should extend beyond fitting 1/16".

Is the fuel tank cap venting correctly ?

[stouchton]

Same exact symptoms as mine has had, numerous possibilities. I proved mine was vapor lock - fuel boiling in carb.

[C26Pinelake]

check to see if gas cap vent is plugged. Wayne

[Tom Endy]

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You don't say what year it is. If it is a 30-31 and has a repo gas cap with a single rivet in the center that could be your problem. They are notorious for the assembly to rotate around the rivet when twisted onto the tank. This blocks off the single vent hole.

There are three different pieces in the assembly, including the gasket, that has the vent hole drilled through. If any one of the three rotates around the rivet, the vent hole is blocked off. This will cause a vacuum in the tank and prevent fuel flow.

It is prudent to modify this type of cap. Drill a small additional hole in all three pieces, being careful not to drill through the top of the cap. Thread it for a 6-32 screw and install the screw with lock-tight or JB weld. This will prevent any one of the three pieces from rotating and blocking off the hole.

Better yet, obtain an Eaton style cap from Snyder that is constructed with two rivets.

Tom Endy

[tackle51]

It is a 1930. Will check gas cap tonight. Patrick L., the fuel screen in tank has the outlet end pushed into the top of the fuel shut-off nipple but don't understand what you are referring to as standard versus 1/2 inch? Also what would cause boiling of gas in carburetor? Radiator is brand new and re-built engine doesn't appear to overheat. Stouchton - how did you correct it? Thanks.

[Tom Wesenberg]

Today's gas (even the good gas without corn crap) boils at a lower temperature than the good gas of the 60's and 70's. The carb gets a lot of heat by being so close to the exhaust manifold that it easily boils in the bowl. This usually happens when at a stop light or driving very slow. Someone made a nice heat shield that bolts above the carb to keep the manifold heat away, and it folds down to keep the exhaust pipe heat away from the intake.

[Chuck Sea/Tac]

If you are getting crud in your filters, then flush your tank. You'll be amazed at what comes out. That's getting to the root of the problem, assuming it's crud stopping fuel flow.
Try disconnecting gas line at carburetor and the turning valve on, dumping into a large container. If the flow is , or gets small, then debris in the tank IS the problem.

[BILL WILLIAMSON]

Tackle,
Believe it or not, I took a 3 hour nap with the Dog & DREAMED about your problem.
A few thoughts: Once Minerva had a tiny black beatle, stuck on top of the float valve, don't know HOW it got there???
I've read in the past that some of the ASSEMBLED float valves have to be taken apart & cleaned out some brass cuttings from the assembly.
When it conks out, remove the carb drain plug & see if the bowl's EMPTY.
Bill W.

[stouchton]

Just as an FYI pertaining to fuel boiling in carb, I spotted it by using the site tube for checking carb fuel level. Left it attached and watched it as the carb heated up. Spotted bubbling and such prior to shut down. Pretty conclusive.

[tbirdtbird]

interesting. and there are those that deny fuel boiling exists. even some right here

[BILL WILLIAMSON]

Originally Posted by tbirdtbird

interesting. and there are those that deny fuel boiling exists. even some right here

Worked for years, on Old Datsuns, with the BIG float chamber window, YES, it's a common occurance!
Bill W.

[Patrick L.]

Originally Posted by tackle51

It is a 1930. Will check gas cap tonight. Patrick L., the fuel screen in tank has the outlet end pushed into the top of the fuel shut-off nipple but don't understand what you are referring to as standard versus 1/2 inch? Also what would cause boiling of gas in carburetor? Radiator is brand new and re-built engine doesn't appear to overheat. Stouchton - how did you correct it? Thanks.

It sounds as though you could do with a good fuel tank flushing. Then install the 'taller' fuel pickup. They are available at most of the vendors and the pickup tube is extended a 1/2" or so just to pickup the fuel above the floor of the tank to allow for more sediment to slosh around in the bottom doing no harm. Also make sure the fuel line doesn't extend too far into the carburetor inlet. I'm one that uses an in-line fuel filter [ between tank and firewall] with no issues. Once I get the carburetor innards clean I like to keep it clean and don't have to worry about the sediment bowl/filter.

As for the fuel boiling, a bakelite spacer between the carburetor and manifold can help as well as a heat shield between manifolds and carburetor. I made mine from aluminum trim coil and it extends from between carb/manifold along the manifold to the exhaust/muffler clamp. It also helps, and may just be the most important, to make sure the fuel line from the firewall travels downhill the full distance to the carb inlet fitting which may require some judicial bending. One member thought some time ago that his boiling issue was that the fuel line was using itself as a ground and was getting hot contributing to the fuel boiling. I'm pretty anal about grounds and use an extra cable from frame to transmitter or bellhousing.

[tackle51]

Patrick L. thanks for the additional information. My in-tank filter is a Snyder's A-9193-T ("gas tank screen"). I assume this is the "taller fuel pickup" that you are referring to? Also I found your comment about being sure the fuel line from the sediment bulb to the carburetor be all "downhill". I've been suspicious that the flow from the tank is not always simply the height of the gas versus the carburetor. After tightening up the glass sediment bowl I've seen the gas only trickle in until I released the vacuum inside the bowl and then re-tightened the glass. Is it possible that the flow is actually a siphon under some circumstances? I've also noticed that the inside fuel line coupling at the sediment bulb nipple is sometimes (always?) leaking after stalling. You and others have given me a lot of intriguing ideas to think about! Thanks so much.

[Patrick L.]

Well, lets just hope we can all figure this problem out.